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During World War I, one of the horrors of trench warfare was a poisonous yellow cloud called mustard gas.
一战时期，有一种黄色的有毒气体，堪称堑壕战里最恐怖的梦魇，它就是“芥子毒气”。
For those unlucky enough to be exposed, it made the air impossible to breathe, burned their eyes, and caused huge blisters on exposed skin.
一旦不幸中招，你将会无法呼吸，双眼灼伤，暴露的皮肤上长出巨大的水泡。
Scientists tried desperately to develop an antidote to this vicious weapon of war.
科学家们穷尽精力，想要研制出能对抗这残暴武器的解毒剂。
In the process they discovered the gas was irrevocably damaging the bone marrow of affected soldiers -- halting its ability to make blood cells.
在这个过程中，他们发现气体对伤员的骨髓造成了永久性损伤，使它无法继续产生血细胞。
Despite these awful effects, it gave scientists an idea.
这一糟糕的结果反而赋予了科学家们灵感。
Cancer cells share a characteristic with bone marrow: both replicate rapidly.
癌细胞和骨髓细胞有一个共同点：它们都能快速自我复制。
So could one of the atrocities of war become a champion in the fight against cancer?
那么，我们能否将战争的暴行变为对抗癌症的武器呢？
Researchers in the 1930s investigated this idea by injecting compounds derived from mustard gas into the veins of cancer patients.
20世纪30年代的研究学者对这个想法进行了验证，他们从芥子气中提取出复合物，再注入癌症病人的静脉里。
It took time and trial and error to find treatments that did more good than harm,
通过长时间反复的试验，他们发现这种方法利大于弊，
but by the end of World War II, they discovered what became known as the first chemotherapy drugs.
而在第二次世界大战末期，人们终于发现了世界上第一种化疗药物。
Today, there are more than 100. Chemotherapy drugs are delivered through pills and injections and use "cytotoxic agents," which means compounds that are toxic to living cells.
如今，市面上的化疗药物高达上百种。患者可以选择口服或者注射，这是一种“细胞毒剂”，即对活细胞有毒的化合物。
Essentially, these medicines cause some level of harm to all cells in the body -- even healthy ones.
虽然，这些药物在一定程度上会损伤身体里的所有细胞，包括健康的。
But they reserve their most powerful effects for rapidly-dividing cells, which is precisely the hallmark of cancer.
但当面对快速分裂的细胞时，打击效果最佳，而那正好是癌细胞的标志。
Take, for example, those first chemotherapy drugs, which are still used today and are called alkylating agents.
举个例子，烷化剂是我们发现的第一种并且至今仍在使用的化疗药物。
They're injected into the bloodstream, which delivers them to cells all over the body.
这是一种注射型药物，被输送到所有细胞内。
Once inside, when the cell exposes its DNA in order to copy it,
当DNA进行自我复制时，
they damage the building blocks of DNA's double helix structure, which can lead to cell death unless the damage is repaired.
它将破坏DNA的双螺旋结构，从而杀死细胞，除非损伤被修复。
Because cancer cells multiply rapidly, they take in a high concentration of alkylating agents, and their DNA is frequently exposed and rarely repaired.
而正因为癌细胞的繁殖速度快，吸引烷化剂大量涌入，DNA在暴露过程中被迅速破坏，很难自我修复。
So they die off more often than most other cells, which have time to fix damaged DNA and don't accumulate the same concentrations of alkylating agents.
所以癌细胞的死亡速度远远高于其他细胞，后者有足够时间自我修复受损的DNA，而不会累积过量的烷化剂。
Another form of chemotherapy involves compounds called microtubule stabilizers.
第二种化疗药物含有一种“微管稳定剂”。
Cells have small tubes that assemble to help with cell division and DNA replication, then break back down.
细胞内的微管聚集后能协助细胞分裂、DNA复制，然后微管散开，完成细胞复制。
When microtubule stabilizers get inside a cell, they keep those tiny tubes from disassembling.
微管稳定剂进入细胞后，它们能阻止已经聚集的微管散开。
That prevents the cell from completing its replication, leading to its death.
从而截断细胞的复制过程，导致细胞死亡。
These are just two examples of the six classes of chemotherapy drugs we use to treat cancer today.
除了上述两种，还有另外四种化疗药物被用于现代癌症临床治疗。
But despite its huge benefits, chemotherapy has one big disadvantage: it affects other healthy cells in the body that naturally have to renew rapidly.
尽管化疗有着巨大的好处，但它有一个明显的缺点：正常情况下迅速代谢的细胞也面临着化疗的巨大杀伤力。
Hair follicles, the cells of the mouth, the gastrointestinal lining, the reproductive system, and bone marrow are hit nearly as hard as cancer.
毛囊、口腔细胞、胃肠黏膜、生殖系统、甚至骨髓，统统都遭受了无差别攻击。
Similar to cancer cells, the rapid production of these normal cells means that they're reaching for resources more frequently
这些正常细胞和癌细胞一样繁殖迅速，也就意味着它们将消耗更多的营养，
and are therefore more exposed to the effects of chemo drugs.
与血管内的化疗药物的反应也更加频繁。
That leads to several common side effects of chemotherapy, including hair loss, fatigue, infertility, nausea, and vomiting.
从而导致化疗的各项副作用，包括脱发、疲劳、不孕不育、恶心、呕吐等。
Doctors commonly prescribe options to help manage these side-effects, such as strong anti-nausea medications.
通常，为了缓解不适，医生会给患者开一些药比如强效的止吐药。
For hair loss, devices called cold caps can help lower the temperature around the head and constrict blood vessels,
有一种冷却帽，专门用于防止脱发。它能降低头皮温度，收缩血管，
limiting the amount of chemotherapy drugs that reach hair follicles.
减少化疗药物与毛囊的接触。当
And once a course of chemo treatment is over, the healthy tissues that've been badly affected by the drug will recover and begin to renew as usual.
一个疗程的化疗结束后，之前受损严重的皮肤组织将恢复健康，重新开始正常的新陈代谢。
In 2018 alone, over 17 million people world-wide received a cancer diagnosis.
仅在2018年，全世界就有超过1700万人被确诊癌症。
But chemotherapy and other treatments have changed the outlook for so many.
幸好，化疗以及其他治疗手段为我们带来了希望的曙光。
Just take the fact that up to 95% of individuals with testicular cancer survive it, thanks to advances in treatment.
超过95%的睾丸癌患者重获健康，而这多亏了医学的进步。
Even in people with acute myeloid leukemia -- an aggressive blood cancer
即使像急性髓系白血病这种严重的血癌，
chemotherapy puts an estimated 60% of patients under 60 into remission following their first phase of treatment.
在接受第一个阶段的化疗后，约60%六十岁以下的患者的病情得到了缓解。
Researchers are still developing more precise interventions that only target the intended cancer cells.
学者们还在继续研究更准确的、只针对癌细胞的干预方式。
That'll help improve survival rates while leaving healthy tissues with reduced harm, making one of the best tools we have in the fight against cancer even better.
以期在提高存活率的同时，减轻对健康组织的伤害，以改进我们拥有的最好的抗癌工具之一。
